Digestion and Nutrition
Digestive System:
Digestion refers to the mechanical and chemical breakdown of foods so that nutrients can be absorbed by cells.
Consists of the ______________________ canal which is all of the organs the food actually passes through and
the __________________ organs that aid in digestion.
Digestion:
What is chemical digestion?
What is mechanical digestion?
Wall of alimentary canal:
The wall of the alimentary canal consists of the same four layers throughout its length, with only slight variations
according to the functions of specific sections of the canal.
The inner layer is the ___________________ that is lined with ________________ attached to connective tissue.
It protects tissues of the canal and carries on secretion and absorption.
The next layer is the __________________ which is made up of ______________ connective tissue containing
blood and lymph vessels and nerves; it nourishes the surrounding layers of the canal.
The ___________________ layer consists of inner ________________ fibers and outer longitudinal fibers that
propel food through the canal.
The outer layer, or ___________________, is composed of visceral peritoneum that protects underlying tissues and
secretes ______________ fluid to keep the canal from sticking to other tissues in the abdominal cavity.
Movements of the Tube
The motor functions of the alimentary canal are of two types--______________ movements and
_______________ movements.
The former movements occur when smooth muscles contract rhythmically in small sections of the tube.
The latter movements include a wavelike motion called ________________________, which is caused by contraction
behind a mass of food as relaxation allows the mass to enter the next segment of the tube.
Mouth:
The mouth is the first portion of the alimentary canal; it functions to receive food and begins ______________
digestion by mastication.
___________________form the lateral walls of the mouth.
The ___________________ are highly mobile structures that surround the mouth opening.
What is their function?
Tongue and teeth:
The tongue is a thick, muscular organ covered by ________________ membrane with taste ________
within _______________; it is attached to the floor of the mouth by the _____________________.
Two sets of teeth develop in sockets within the alveolar processes of the _________________and
_________________ bones.
How many primary teeth are there?
How many secondary?
What is the function of the teeth?
Different teeth are adapted to handle food in different ways, and include incisors, cuspids, bicuspids, and molars.
Each tooth consists of a crown and a root. What are they made of?
A tooth is held tight in its socket by a ______________________ ligament.
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Palate:
The palate forms the roof of the oral cavity and has an anterior __________ palate and posterior _________ palate.
The latter and a flap called the _______________ function to close off the nasal cavity during swallowing.
Tonsils:
Associated with the palate in the back of the mouth are _______________ tonsils, which , because they are
____________________ tissue, help to protect the body against infection.
Another lymphatic tissue mass, _______________ tonsils (adenoids), are located on the posterior wall of the
pharynx, above the border of the soft palate.
__________________ tonsils are lymphatic tissues located at the root of the tongue.
Salivary glands:
The salivary glands secrete ________________, which moistens and dissolves food particles, binds them together,
allows tasting, helps to cleanse the mouth and teeth, and begins __________________ digestion.
Salivary glands contain ____________cells that produce a watery fluid with an enzyme called _______________,
and ___________________ cells that produce lubricating and binding fluid.
Salivary glands receive parasympathetic stimulation that triggers the production of a large volume of saliva at the
_____________ or __________________ of food.
The ______________________ glands, lying in front of the ear, are the largest of the major salivary glands; they
secrete a clear, watery fluid rich in amylase.
The _________________________ glands, located on the floor of the mouth, secrete a more viscous fluid.
The _______________________ glands, inferior to the tongue, are the smallest of the major salivary glands and
secrete a saliva that is thick and stringy.
Pharynx:
The pharynx is a cavity lying behind the mouth. It functions in both the _______________ and ________________
systems.
The pharynx connects the nasal and oral cavities with the larynx and esophagus and is divided into a
________________ (top portion), _________________ (middle portion), and __________________
(bottom portion).
Swallowing Mechanism
Swallowing reflexes can be divided into three stages.
Food is mixed with saliva and voluntarily forced into the ________________ with the tongue.
Sensory receptors here sense food, which triggers swallowing __________________.
In the third stage of swallowing, __________________ transports the food in the esophagus to the ____________.
Esophagus:
Mucous glands are scattered throughout the ______________of the esophagus and produce mucus to moisten and
lubricate the inner lining of the tube.
The lower ________________ sphincter helps to prevent regurgitation of the stomach contents into the esophagus.
Stomach:
The stomach is a J-shaped muscular organ that receives and _________ food with digestive juices, and _________
food to the __________________ __________________.
The stomach is divided into cardiac, fundic, body, and pyloric regions and a pyloric canal. Be able to identify and
locate these parts.
A _________________________ sphincter controls release of food from the stomach into the small intestine.
Gastric secretions & functions:
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________________ glands within the mucosa of the stomach open as ______________ pits.
These glands generally contain three types of secretory cells.
______________________ cells produce thick fluid that protects the stomach lining.
______________ cells secrete ____________ (to digest protein) as inactive ________________, which is activated
when it comes in contact with ___________________________ acid.
__________________ cells secrete this acid.
Other components of gastric juice include _______________ factor, required for vitamin B12 absorption from the
small intestine.
Gastric Absorption
The stomach absorbs only small quantities of water and certain __________, alcohol, and some lipid-soluble ______.
Mixing and Emptying Actions
Following a meal, mixing actions of the stomach turn the food into ______________ and pass it toward the pyloric
region using _________________ waves.
What does the rate at which the stomach empties depends upon?
As chyme fills the duodenum, stretching of its wall triggers the ________________ reflex, which inhibits
peristalsis and slows the rate at which chyme enters the small intestine
Regulation of Gastric Secretions
Gastric secretions are enhanced by parasympathetic impulses and the hormone ______________, which is released
from gastric glands.
As more food enters the small intestine, secretion of gastric juice from the stomach wall is reflexly inhibited.
Presence of ________________ and proteins in the upper small intestine causes the release of ____________ from
the _____________________ wall, which also decreases gastric mobility.
Pancreas:
The pancreas has an ________________ function of producing pancreatic juice that aids digestion.
The pancreas is closely associated with the ________________ intestine.
The cells that produce pancreatic juice, called pancreatic ____________ cells, make up the bulk of the pancreas.
These pancreatic cells cluster around tiny tubes that merge to form larger ones, and then give rise to the
_______________ duct.
The pancreatic and __________ ducts join and empty into the small intestine, which is surrounded by the
_________________________ sphincter.
Secretions & functions of the pancreas:
Pancreatic juice contains _____________________ that digest carbohydrates, fats, proteins, and nucleic acids.
List the pancreatic enzymes.
Protein-digesting enzymes are released in an ______________ form and are activated upon reaching the small
intestine.
Regulation of Pancreatic Secretion
The nervous and endocrine systems regulate release of pancreatic juice.
___________________from the duodenum stimulates the release of pancreatic juice with a high bicarbonate ion
concentration but few digestive enzymes.
______________________ from the wall of the small intestine stimulates the release of pancreatic juice with
abundant digestive enzymes.
Liver:
The reddish-brown liver, located in the upper ___________ quadrant of the abdominal cavity, is the body’s largest
internal organ.
The liver is divided into right and left ______________, and is enclosed by a fibrous capsule.
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Each lobe is separated into ____________ lobules consisting of ____________cells radiating from a central vein.
Hepatic ___________________ separate groups of hepatic cells.
Blood from the hepatic________________ vein carries blood rich in nutrients to the liver.
__________________ cells carry on phagocytosis in the liver.
Secretions from hepatic cells are collected in __________ canals that converge to become hepatic ducts and finally
form the __________________ __________________ duct.
Bile:
Bile is a yellowish-green liquid that ________________ cells secrete; it includes water, bile salts, bile pigments,
cholesterol, and electrolytes.
Bile pigments are breakdown products from ______________ blood cells.
Only the bile ________________ have a digestive function.
Liver Functions
The liver carries on many diverse functions for the body.
The liver is responsible for many ________________activities, such as carbohydrates, lipids, and proteins.
The liver also stores glycogen, vitamins ______, ________ and ___________, iron, and blood.
The liver filters the _______________, removing damaged red blood cells and foreign substances, and removes
_________.
The liver's role in digestion is to secrete _______________.
Gall bladder:
It is connected to the _______________ duct, which joins the hepatic duct; these two ducts merge to form the
_____________ ______________ duct leading to the duodenum.
A sphincter muscle controls the release of bile from the common bile duct.
function & regulation:
Bile does not normally enter the duodenum until __________________stimulates the gallbladder to contract.
The _______________ sphincter remains contracted unless a peristaltic wave approaches it, at which time it relaxes
and a squirt of bile enters the duodenum.
Bile salts emulsify ______________ into smaller droplets and aid in the absorption of fatty acids, cholesterol, and
certain __________________.
Small intestine:
The lengthy small intestine receives secretions from the ____________ and ____________, completes digestion of
the nutrients in ________________, absorbs the products of digestion, and transports the remaining residues to the
________________ intestine.
The small intestine consists of what three parts?
The __________________ is the shortest and most fixed portion of the small intestine; the rest is mobile and lies free
in the _________________ cavity.
The small intestine is suspended from the posterior abdominal wall by a double-layered fold of peritoneum called
______________________________ .
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Structure of the Small Intestinal Wall
The inner wall of the small intestine is lined with finger-like intestinal ______________, which greatly increase the
surface area available for _______________________and aid in mixing actions.
Each ______________ contains a core of connective tissue housing blood capillaries and a lymphatic capillary
called a _______________________.
Between the bases of adjacent villi are tubular intestinal glands.
Functions of small intestine:
Cells that secrete mucus in the small intestine include ______________ cells, which are abundant throughout the
mucosa, and mucus-secreting glands located in the ___________________ of the duodenum.
Intestinal glands at the bases of the villi secrete large amounts of watery fluid that carry digestive products into the
villi.
Epithelial cells of the mucosa have embedded digestive enzymes on their tiny hairlike ______________. What are
these enzymes?
Regulation of Small Intestinal Secretions
Mechanical and chemical stimulation from chyme causes goblet cells to secrete mucus.
Distention of the intestinal wall stimulates _______________________ reflexes that stimulate secretions from the
small intestine.
Absorption in the Small Intestine
The small intestine is the major site of absorption within the alimentary canal.
Simple sugars called ______________________ are absorbed by the villi through active transport or ____________
diffusion and enter ____________________ capillaries.
Building blocks of proteins, ____________ acids are absorbed into the villi by active transport and are carried away
in the ________________.
Fatty acids are absorbed and transported differently than the other nutrients.
Fatty acid molecules ________________ into the cell membranes of the villi.
The _______________________________ of the cells reconstruct the lipids.
These lipids collect in clusters that become encased in protein (_______________________).
These clusters are carried away in ______________ _____________ until they eventually join the bloodstream.
The intestinal villi also absorb water (by ________________) and electrolytes (by ____________ ____________).
Large intestine:
The large intestine absorbs _______________ and __________________ and forms and stores ____________.
The large intestine consists of the __________ (pouch at the beginning of the large intestine), ____________
(ascending, transverse, descending, and sigmoid regions), the ____________, and the ___________ canal.
The anal canal opens to the outside as the anus; it is guarded by an involuntary ____________ _______ sphincter
and a voluntary external ______________ _______________ muscle.
Structure of the Large Intestinal Wall
The large intestinal wall has the same four layers found in other areas of the alimentary canal, but lacks many of the
features of the small intestinal mucosa such as villi.
Fibers of longitudinal muscle are arranged in _____________ __________ that extend the entire length of the colon,
creating a series of pouches (__________________).
Functions of the Large Intestine:
The large intestine does not digest or absorb nutrients, but it does secrete mucus. The large intestine absorbs
___________________ and water.
The large intestine contains important _______________that synthesize vitamins and use cellulose.
________________ are composed of undigested material, water, electrolytes, mucus, and bacteria.
Both their color and odor is due to the action of bacteria.
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Nutrients:
________________ is the process by which the body takes in and uses nutrients.
___________________ nutrients are those that cannot be synthesized by human cells.
Carbohydrates:
Carbohydrates, such as sugars and starches, are organic compounds used for sources of ___________ in the diet.
Carbohydrates are ingested in a variety of forms, list some of these forms.
During digestion, complex carbohydrates are broken down into __________________, which can be absorbed by
the body.
__________________ is a complex carbohydrate that cannot be digested, but provides bulk (fiber), facilitating the
movement of food through the intestine.
Carbohydrate Utilization
The monosaccharides that are absorbed in the small intestine are fructose, galactose, and glucose; the liver converts
them all into ___________________.
Excess glucose is stored as ______________ in the liver or is converted into ___________ and stored in adipose
tissue.
Certain body cells (neurons) need a continuous supply of glucose to survive; if glucose is scarce, _______________
_______________ may be converted to glucose.
Carbohydrate Requirements
The need for carbohydrates varies with a person's _________requirements; the minimum requirement is unknown.
An estimated intake of _______________grams of carbohydrate is needed daily to avoid protein breakdown.
Lipids:
Lipids are organic substances that supply ____________ for cellular processes and to build structures.
The most common dietary lipids are ________________.
Lipids include ______________, ___________________ for cell membranes, and ___________________.
____________________ are found in plant- and animal-based foods. Where are saturated fats found?
Unsaturated fats?
Cholesterol?
Lipid Utilization
Digestion breaks down ___________________ into fatty acids and ________________.
The ______________ and adipose tissue control triglyceride metabolism that has many steps.
The _____________ can convert fatty acids from one form to another, but it cannot synthesize the __________
fatty acids that must be obtained from the diet.
The ___________ controls circulating lipids and cholesterol.
Excessive lipids are stored in ______________________ tissue.
Lipid Requirements:
Human diets vary widely in their lipid content. A typical diet consisting of a variety of foods usually provides
adequate fats.
Proteins:
Proteins are polymers of _____________acids with a wide variety of functions in cells and in the body. List
these functions.
Animal sources of protein contain _________________ proteins, which contain all ____________ amino acids.
Plant sources of protein are missing one or more essential amino acids making them _____________ proteins that
should be consumed in combinations.
Protein Requirements:
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Protein requirements vary according to body size, ________________ rate, and _______________ requirements.
For the average adult, nutritionists recommend __________ grams of protein per day per kilogram of body weight;
pregnant and nursing women need more.
Vitamins:
Vitamins are organic compounds required in small amounts for normal metabolic processes, and are not produced by
cells in adequate amounts.
Vitamins are classified as __________-soluble (vitamins A, D, E, and K) or __________-soluble (B vitamins and
vitamin C).
Fat-Soluble Vitamins:
Fats-soluble vitamins dissolve in fats and are influenced by some of the factors that influence lipid absorption.
Fat-soluble vitamins are stored in moderate quantities in the body and are usually not destroyed by cooking or
processing foods.
What are the functions of the 4 fat soluble vitamins?
Water-Soluble Vitamins:
Water-soluble vitamins, including the B vitamins and vitamin C, are necessary for normal cellular ______________
in the oxidation of carbohydrates, lipids, and proteins.
Vitamin ______ (ascorbic acid) is needed for the production of ______________, the metabolism of certain _______
________________, and the conversion of folacin into folinic acid.
What are the functions of the B vitamins?
Minerals:
Dietary minerals are derived from the soil and are essential in human metabolism.
Minerals are responsible for ________%of body weight, and are concentrated in the ___________ and __________.
Minerals may be incorporated into organic molecules or inorganic compounds, while others are free ions.
Minerals comprise parts of the structural materials in all body cells, where they may also be portions of __________ ;
they contribute to the ____________ pressure of body fluids and play roles in conduction of________________,
_______________ contraction, ________________ of blood, and maintenance of ____________.
Major Minerals:
____________and _____________ account for 75% by weight of the minerals, and are thus called major minerals.
What are the other major minerals?
Trace Minerals:
Trace elements are essential nutrients needed only in minute amounts, each making up less than 0.005% of adult body
weight.
List them.
Adequate Diets:
An adequate diet provides sufficient energy as well as adequate supplies of essential nutrients to support growth,
repair, and maintenance of tissues.
_______________ is poor nutrition that results either from a lack of essential nutrients or a failure to utilize them;
it may result from undernutrition or overnutrition.
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